Loaded-sttbmarine-cable telegraph system



Patented Nov. 1, 1927.

4UNITED Nsriiriss 1,641,267 PATENT OFFicE.

OLIVER E. EUCKEEY, OE MAPLEWOOD, NEW JERSEY, Assieiion To WEsrEEiv ELEO- 'rnio OoivirANY,rNconronArED, `OE NEW YORK, iv. Y., A CORPORATION or MEW YOEK.

nOAnEn-sUEMARINE-OABLE TELEGRAPH SYSTEM.

Application led August 14, 1924. Serial No. 731,897.

This invention relates to submarine telegraphy over a loaded submarine cablenand more particularly to a method for eliminating distortion due to magnetic hysteresis in the loading material. i

In a loaded submarine cable, as for example, in the type of cable described in applicants Patents 1,586,874 and 1,586,87 5, granted J une l, 1926, signals are attenuated and; distorted in a manner different from that in ordinary non-loaded cables. The addition ot inductance serves to counteract in a degree the ei'lect ot' the capacity in attenuating and distorting the signals, but at the same t-iine introduces nevv'sources of distortion. These arise chiefly from the effective resistance introduced byeddy currents and hysteresis in the` nickel-iron alloy or other loading material used for adding inductance. rlhe eti'ect of eddy currents is to cause greater attenuation of the high'frequency component-s of vthe signals. This type of distortion may be reduced by the use of thin laminations ot loading material and by compensating networks Which tend to restore the various ifrequency components to t-heir original relative amplitud-es.

The effect ot hysteresis is only telt with relatively great strength of sending current and is introduced principally at the sending end lof-tliecable Where the currentis large compared to its value at the receiving end. This `is because hysteresis loss increases rapidlyV lWith increasejof currentstrength and disappearsivhen the current ainplitude approaches jzero. IThe distortionintroduced by liysteresisis peculiar in that With certain types of signals such` as,` for instance, signals in the standard three-element cable codeitr is asymmetrical as Will be explained hereinafter. One Way to Vavoid hysteresis distortion lis; to use a lovv sending voltage in the cable conductor. However, to secure` Which Willlresult in small current strength the maximum speed of operation of a cable Y it is desirable to use as'high a sending volt- `To this end telegraph signals are transmitted over a loaded cable by means ot a tivol element code. In such a code positive and negative impulses of equal amplitudes are impressed upon the cable for each signal element. Spaces are indicated by current of one polarity, While dots and dashes are indicated by current of the opposite polarity. Dots are distinguished from dashes by the time interval of the application oi' the impressed potential. The principle Ot' operation ivill `be explained hereinafter.

The novel features Which are considered characteristic of this invention are set toi-th With particularity in the appended claims. The invention, both as to its organization and operation together With other Objects and advantages thereof, Will be further explained hereinafter, having reference to the accompanying' drawing, consisting of the following figures: y

Fig. 1 is a circuit diagram showing schematically one embodiment of the invention.

Fig. 2 is a typical B-H curve of the magnetic material used to load the cable ot Fig. l.

Fig. 3 illustrates Wave forms involved in signaling With the tivo-element code.

Fig. tillustrates Wave forms involved in signaling With a three-element code.

Proceeding "now to` a detailed description of one embodiment of the invention, and referring first to Fig. l, a loaded cable 5 coiistitutes a transmission circuit between sending apparatus S and receiving apparatus R. 90` Sending apparatusS is adapted to transmit .i signalsV according tO a`tWo-eleinent code. Current is supplied by battery (iuiider the control ot relays 7 and S, the armaturesv ot which determine the polarity Which is im- 95 pressed upon the cable 5. rl`he relays 7 and 8 are energized simultaneously by current from battery 9 When key l0 is depressed. The sending end Condenser ll is connected into the transmission circuit` between the 10o armature of relay 7 and the cable 5. `liiith key lO open (as shown) negative potentialv from` battery 6 is impressed upon the sending end condenser l1. Then key l0 is closed and relays 7 and 8 are energized to attract 105 their armatures, positive potential is impressed upon the sending condenser 11.

At the receiving terminal, electron discharge devices l2 and lf3 are employed to amplify the incoming signals :tor operating Ilo Y Big.

a recording device 14, which may be a syphon recorder as indicated. lliave shap ing networks 15 are employed in the manner described inthe copending applications of Oliver E. Buckley supra. Other suitable re ceiving terminal apparatus, such as that disclosed in a patent to A. M. Curtis 1,566,970,

`granted J une 1, 1926, may be used.

curve is shown.` Vihen a two-element code is used for signaling, the Wave shape of the applied potential will be like that `shoivn in curve A of Fig. 3. Due to the sending condenser 11, the Wave shape ot' the current near thev sending end of the cable 5 will be substantially that shown in curve B ot Fig. 3.

Suppose now that the field H ot Fig. 2 corresponds to the current l iii curve B ot Then the pulse 1 will carry the inagnetizatioii of the loading material through zve c l a, assuming` that it already has rlhe next impulse 2,

sive remanence. beingjot opposite sign, Will carry it through the curve a l) c. The third impulse will carry' it through the curve c d a again. Since successive impulsesV are ot opposite polarity and since all ot the impulses give the same degree of change of induction, each impulse ivill'give the same'induced electromotive force and the same strength ot propa' gatedsigiial. lhere will, theretore,`be no asymmetrical magnetic distortion due to hysteresis.

`Considering, however, the case otsignal` ing" by meansof three-element signals as used in the standard cable code, the wave shapel of the applied electromotive itorcebeingl shown byl curve C of 4, the Wave shape of the current near the sending end of L the cable 5, due tothe action of the sending end condenser 11Will be that shown in curve D of Fig. 4. Starting again with a remanence o as bet'ore,`iinpulse 1 will carry the magnetic material through the curve c da, The second impulse Will carry it through the curve a 5 o.V lmpulse'?) will carry it again Vthrough curve c Z a and impulse 4 throughl curve a 5 c." The impulse 5, hovvever, being of the same polarity asin pulse 4, ivill carry the material only over the dottedcurve c y c, giving onlyA a very small change of inductionrelativeto that given by impulse 4, and consequently a relatively Weak transmitted impulse along the cable. The same eii'ect will occur again at impulse 7 following impulse 6, both ot which are of the same polarity. y

The eilect upon the received signals will now be described. In either type ot signaling there will be distortion in the received signals, which will need to be corrected. As will hereinafter, however, appear this can be easily accomplished in the case ot two elenient Working VThe ditliculty encountered in three clement operation is caused by the sending end ofthe cable acting as a loiv inductance loaded cable when the current in `the cable changes from maximum to zero or when the current changes from Zero to a maximum of the saine sign as the preceding maximum, While, in the cases Where the current changes from zero to a maximum ot' sign oppositeto the preceding maximum, the cable acts as a. high inductance loaded cable. ln the caso ot the current impulses involved in the tivoelement code, as .shown in Fi 3 curve B, this means that the iii-st halt ot each ol?y the pulses, that is the change from zero to mari mum current, Will be transmitted as over a cable ot much higher inductanee than the apparent inductance ot the actual cable, while the second halt-oit each pulse, that is a change i'from maximum to Zero current, Will be received as though ithad been transmitted over a cable oi smaller inductaiice than that ot the actual cable. There is therefore distortion present in the t\voelcment system oi signaling, butit atliects all signals alike and therefore does not cause confusion in interpreting the received message. Vlhere ivillprobably be involved in cach signal a small irregularity which probably would shoT up more at higher values ot signaling speeds than at the lower.

Referring to Fig, 4 curve D, it can be seen that inthe case oit signals in the threeelement code, there Will be, in addition to the distortion just describethan additional distortion due to the tact that entire current pulses of the; type 5, 6 or 7, 8 are received as thouglithey had been transmitted over a loiv inductance cable. This means that at every point in they message Where the current changes irom zero to a maximum value ot opposite sign from the preceding signal pulse, the initial height and slope oi such a signal will be different from that ot the other signals and this distortion cannotbe corrected by shaping networks Without distorting the remaining signal pulses. The point at Which thisdistortion takes place is exactly the place Where maximum clear ness is necessary.

A type ot distortion Will thus he introduced in .three-element Working which would be abseiitwith tivo-element Working. From the foregoing description it: is seen that titl [lll

lill) troublesome hysteresis distortion is eliminated by the use of a two-element code in connection with loaded submarine cables.

The invention is not limited to the specific elements shown in Fig. l. Modifications thereof Will be obvious to those skilled in the art. The scope of the invention is defined by the appended claims.

l/Vhat is claimed is:

l. The method of signaling over a submarine cable loaded with magnetic material for increasing the inductance thereof, said magnetic material introducing hysteresis loss at the magnetic densities involved in transmission, Which comprises employing a two-element code for transmission.

2. The method of reducing signal distortion When signaling over a submarine cable loaded with magnetic material for increasing the inductance thereof, said material being such as to introduce hysteresis loss at the magnetic densities involved in transmission,

which comprises applying potential impulses to the cable in such order that each of the resultant current impulses causes the loading material to pass through a magnetization cycle substantially identical With the cycle resulting from any and every other current impulse of the same polarity.

3. In a submarine telegraph system employing for transmission a submarine cable loaded with magnetic material of suiiicient permeability to increase the possible signaling speed as compared with an unloaded cable, the method of reducing signal distortion caused by hysteresis effects in the loading material Which comprises applying to the cable successive signaling impulses of alternately opposite potential but of equal amplitude.

4. In a signaling system, a long cable, magnetic material used to load said cable, means to apply successive impulses of direct current to said loaded cable for signaling, successive impulses being of opposite polarity but equal amplitudes, and receiving means for said signals.

5. In a submarine telegraph signaling system, a long submarine cable loaded with magnetic material having appreciable hysteresis at the current amplitudes used for telegraphing, sending apparatus adapted for applying impulses of current to said cable according to a` tivo-element code, and receiving apparatus for receiving said signals.

6. In a submarine telegraph signaling system, a submarine cable loaded with a nickeliron alloy having a permeability appreciably higher than that of iron, sending apparatus adapt-ed for applying impulses of current to said cable according to a two-element code, and receiving apparatus for receiving said signals.

7. In a submarine telegraph signaling system, a submarine cable at least a thousand miles long loaded with nickel-iron alloy, sending apparatus adapted for 'applying impulses of current to said cable according to a two-element code, and receiving apparatus for receiving said signals.

In Witness whereof, I hereunto subscribe my name this 11th day of August, A. D., 1924.

OLIVER E; BUCKLEY. 

